In a way,these can be said to be a form of censorship or miseducation. I (funny enough) am in high school (in United States) currently and the mass amount of these things (aside from Columbus and the Holocaust) haven't been taught to us in Middle School. Vietnam seems to be avoided entirely, the Great Depression is just mentioned, and to be honest the classes make America's history seem flawless. The only thing negative mentioned about the Indians I've heard from school is the "trail of tears" and that has been downplayed.